The present invention relates to a telescoping joint used at the top of a riser extending from a subsea wellhead to the surface which allows relative motion between the riser mandrel and the telescoping tubular mandrel and to an improved packer positioned between the riser mandrel and the telescoping mandrel. In prior risers telescoping joints have been used to provide such relative motion. Such telescoping joints have included resilient packers which include apparatus for the introduction of a fluid under pressure to exert a controlled force on the exterior of the packer to seal against the hydrostatic head of mud. In such prior structures the pressure introduced was controlled to allow a limited leakage of mud past the packers for lubrication purposes.
Recently specifications have been adopted which require telescoping joint packers to be able to seal against pressures up to 200 psi. Additionally, some operators are requesting that the telescoping joint packers have the ability to seal against pressures up to 500 psi. Such high sealing pressures exerted on the resilient packer prevents any lubricating leakage of mud past the packing. This results in high packer wear rates and in some extreme cases may prevent the relative motion between the telescoping mandrel and the riser mandrel.
U.S. Pat. Nos. 2,071,197, 2,746,709, 2,,843,349 and 3,492,007 all disclose blowout preventers for use on a well in which the packer is activated into its sealing position responsive to fluid pressure applied thereto.
U.S. Pat. No. 2,176,355 discloses a drilling head having an annular resilient packer sleeve which is adapted to close around a kelly when it is exposed to external pressure.
U.S. Pat. No. 2,192,805 discloses casing head seals in which pressure is supplied through an annular metal sleeve to the exterior of an annular flexible packer to provide sealing against the string extending therethrough.
U.S. Pat. No. 1.458,270 discloses a flexible seal which is inflated to be a wiper seal against the exterior of a pump rod.
U.S. Pat. No. 3,471,156 discloses an inflatable packing for a stuffing box in which the interior of the packing is provided with a plurality of annular recesses to provide a plurality of lip seals which seal against the rod extending through the box.
None of this prior art suggests any structure which is similar to the improved structure of the present invention nor do they have any appreciation of the problem which has been solved by the present invention of providing a high pressure seal without excessive friction and wear as hereinafter explained.